A lithography technique is used to form a desired circuit pattern in a semiconductor device, and a pattern transfer using an original pattern called a mask (a reticle) is performed in the lithography technique. For this technique, an electron beam drawing technique exhibiting excellent resolutions is used to manufacture a reticle with high precision.
One of methods for a charged particle beam drawing apparatus configured to perform the electron beam drawing on the reticle is a variable shaped beam method as below. Specifically, although not illustrated herein, in the variable shaped beam method is a method in which a pattern is drawn on a workpiece placed on a movable stage by using an electron beam shaped through first and second shaping apertures.
Here, by using two stages of main and sub deflectors for positioning a beam on a substrate by deflection, the pattern drawing process is performed in each of stripe fields into which a drawing region on the substrate is divided in a strip form. The stripe field has a width in which the main deflector can position the beam by deflection. Further, when each stripe field is drawn, the drawing is performed in each of sub-deflection fields into which the strip field is divided in a mesh form. The sub-deflection field has a size in which the sub deflector can position the beam by deflection. The aforementioned stripe width and the sub-field have been made smaller and smaller, as techniques for higher precision and further miniaturization have been advanced in recent years.
The increase of the number of the stripes and the downsizing of the sub-fields along with the downsizing of the width of each stripe influence the drawing accuracy. Correction in the sub-deflection areas is described in Japanese Patent Application Publication No. 2011-066236.
In addition, the above trends are also influencing settling in main deflection fields. The settling in the main deflection fields has conventionally been performed in the following manner, for example. Specifically, FIG. 9 shows a part of an evaluation substrate 100 used for measuring position errors required in calculation of settling conditions in main deflection fields 101. FIG. 9 particularly shows one main deflection field 101 in an enlarged manner.
The evaluation substrate 100 has measurement patterns 102 drawn thereon which are used to measure position errors. In FIG. 9, the measurement patterns 102 are shown in squares and drawn at 10 positions in an X direction and at 11 positions in a Y direction, that is, at 110 positions in total in the one main deflection field 101. Here, the number of measurement patterns to be drawn in one main deflection field can be set to any number.
In the main deflection field 101 shown in FIG. 9, the first measurement pattern is drawn in the lower left corner, and then the measurement patterns are drawn one after another in the Y direction at regular intervals, as shown by solid line arrows. After a line of the main deflection field 101 in the Y direction is full of the drawn measurement patterns, the charged particle beam moves to the lower right (an XY stage having the evaluation substrate 100 placed thereon moves), so that the measurement patterns are again drawn in the Y direction.
By performing such drawing, the settling condition is calculated based on the position errors in the drawing using the charged particle beam in cases where the charged particle beam moves in a long distance (moves to the lower right for the next column after completion of the drawing of all the measurement patterns in one column), and in contrast in a short distance (moves to draw the measurement patterns in the same column in the Y direction).
However, the main deflection settling explained by using FIG. 9 described above could be made even with higher accuracy in terms of the following point.
Specifically, the method of drawing measurement patterns shown in FIG. 9 can obtain measurement data of only two distances of the long and short moving distances of the charged particle beam. As a matter of course, data of various distances can be analogically obtained based on the measurement data of the two distances, and thus the settling condition can be calculated actually. However, when highly accurate main deflection settling is also required as described above, the measurement data of only the long and short distances might be insufficient to calculate the settling condition.
Hence, employment of the following method is conceivable as the method of drawing measurement patterns. FIGS. 10 and 11 are exemplary diagrams for explaining methods of drawing measurement patterns different from the drawing method shown in FIG. 9, and respectively show the drawing methods different from each other. Numbers indicating the order of the drawing are put in the squares of some of the measurement patterns 102.
In FIG. 10, the drawing of the measurement patterns 102 is started at the lower left corner of a main deflection field 101A. After a measurement pattern 102A denoted by the number 1 is drawn, a measurement pattern 1028 denoted by the number 2 is drawn in an area farthest from the measurement pattern 102A in the same column. After the measurement pattern 102B is drawn, a measurement pattern 102C which is adjacent to the measurement pattern 102A and denoted by the number 3 is drawn.
As described above, in the main deflection field 101A shown in FIG. 10, the drawing start position is set to a measurement pattern closest to a corner. Next, the drawing is performed in a drawing area located farthest from the drawn measurement pattern in the same column. As the result, the drawing is performed back and forth in the same column in the Y direction, that is, in the order of the assigned numbers in FIG. 10. After the measurement patterns are drawn in all the areas set in the same column, the drawing is performed in the next column in the same manner.
In contrast, the drawing method shown in FIG. 11 uses the same drawing start position as the method described by using FIG. 10 in the drawing start position but is different in the order of drawing. Specifically, in a main deflection field 101B shown in FIG. 11, the drawing is started at a measurement pattern 102a located in the lower left corner of the main field 101E and denoted by the number 1. Next, a measurement pattern 102b denoted by the number 2 is drawn. Further, the subsequent drawing is performed at a position (a measurement pattern 102c denoted by the number 3) located adjacent to the measurement pattern 102a in the same column as the measurement pattern 102a denoted by the number 1. After the measurement pattern 102c is drawn at the position denoted by the number 3, the drawing is performed at a position (a measurement pattern 102d denoted by the number 4) located farthest from the measurement pattern 102c in the same column as the measurement pattern 102c. This position is located adjacent to the measurement pattern 102b in the same column as the measurement pattern 102b. 
The drawing is continued in the X direction as described above until none of the measurement patterns 102 is left for the drawing. Then, the charged particle beam returns to the column including the measurement pattern 102a, and the drawing is performed in the next line in the same manner, starting at a measurement pattern 102 denoted by the number 21.
Employment of the method shown in FIG. 10 or 11 makes it possible to evaluate the settling not only in the long and short distances but also in the various distances, and thus to calculate a highly accurate settling condition through the evaluations.
Nevertheless, the methods shown in FIGS. 10 and 11 can calculate the settling condition in the various distances, but are considered to have another inconvenience. Specifically, in either of the methods, the charged particle beam firstly moves in the long distance to perform the drawing, and then the moving distance required for the drawing is gradually made shorter. In this case, a settling time might be insufficient in the start stage of the drawing. In consideration of this, the drawing progresses successively while being in short of the settling time. As a result, the drawing is performed in a position displacement state attributable to the insufficient settling time. This prevents accurate evaluation.